The present invention pertains to novel strains of lactic acid bacteria capable of reducing an individual's tendency to develop allergic reactions. In particular, the present invention relates to recombinant strains of lactic acid bacteria expressing surface polypeptides which include small and larger peptides acting as mimics for at least a part of the Fc region of immunoglobulin E (IgE)-molecules. The invention also pertains to food or pharmaceutical compositions containing said micro-organisms or active fractions thereof.
The immune system is a complex and multifactorial defense system that protects the body from any invasive biological or chemical agent, such as viruses, bacteria, parasites and fungi or simply larger chemical substances. Although being indispensable for maintaining the body's integrity, the immune system may in certain cases be the cause of the illness itself, such as in autoimmune diseases, inflammation or allergies.
Allergies are inappropriate reactions of the immune system to a variety of substances (allergens). Generally, individuals do not generate a significant immune reaction against substances regularly encountered in the environment, such as pollen or food material, which non-reactivity is deemed to be mainly due to a suppressing mechanism of the immune system itself However, in an impaired condition the immune system does not fulfil said suppressing activity resulting in a specific immune reaction against the allergen—the allergic reaction.
A generally established mechanism of allergic reactions involves a sequence of events beginning with the uptake of the allergen which needs to pass the epithelial barrier to reach and activate effector cells, located in the lamina propria or epithelium below the level of the tight junctions. The clinical symptoms associated with allergic reactions are basically the result of an early specific immune response and a late inflammatory reaction. During the early phase immunoglobulines E (IgE) against the allergenic substance are produced by the host's immune system, which are subsequently bound via a receptor protein to e.g. mast cells and basophils. Upon binding and crosslinking the IgE molecules on their surface the cells release histamine and cytokines, which then mediate the late phase by recruiting inflammatory cells into the nasal and upper respiratory tract passages. The influx of eosinophils, macrophages, lymphocytes, neutrophils and platelets subsequently starts the inflammatory cycle amplifying the initial immune response which in turn triggers the release of more inflammatory cells.
In the past, the number of individuals suffering from allergy has increased, which is frequently attributed to an ever increasing atmospheric pollution caused by e.g. exhaust gases. Also, an extended consumption of proteinaceous material is deemed to contribute to said development, in particular to the growing occurrence of food allergy. Further, the deficit in microbial infections encountered in developed countries has also been suggested as another possible cause for the increase of atopic diseases.
Therefore, there exists a need in the art to treat allergy, for which different approaches have been proposed so far.
As for the treatment of food allergy some methods rely on modifying the food material itself such that its allergenic potential is reduced. This may be achieved by altering the chemical structure thereof, or by limiting or banning the food material or components thereof, respectively, which would be the cause of such trouble. Yet, a problem involved often resides in that the specific allergenic substance in the respective food material is frequently not known so that in most cases it is not clear which component should be selectively removed or altered.
A different approach of treating food allergy and food intolerance is directed to restoring and maintaining the intestine's integrity such that food allergens essentially may not pass. In this respect, U.S. Pat. No. 5,192,750 describes the use of N-acetyl glucosamine to enable the mucosa to form the necessary barrier to transmission of food allergens and to maintain normal function.
A most general approach of treating allergy is an immunotherapy which involves repeated injection of the allergen, over a period of several years, to desensitize a patient to the allergen. Proceeding accordingly is, however, time consuming, involves years of treatment, and often fails to achieve its goal of desensitizing the patient.
According to a more recent approach, vaccination of individuals against IgE molecules is suggested which inhibits triggering of mast cells and basophils. To this end, WO 97/31948 proposes specific peptides for vaccination that resemble in their three dimensional conformation parts of the IgE molecule, i.e. the immunoglobulines involved in the release of mediators, that play a part in the regulation of allergic and inflammatory reactions. It is conceived that the individual's own immune system will eventually form antibodies directed to said IgE molecules such that said IgE immunoglobulines are scavenged.
However, said method harbours the disadvantage common to normal vaccination procedures in that the biologically active substance has to be administered by invasive methods, such as e.g. by intraveneous injection, which route of administration is generically disliked by patients. On the other hand, when choosing the oral route, suitable galenic formulas have to be designed to allow the biologically active substance to pass the gastro-intestinal tract without getting destroyed. Another problem encountered in this method resides in that the mimotopes are, in most of the cases, short length peptides, that on their own will not elicit a substantial immune response so that apart from carriers and excipients adjuvantia have to be included in the composition.
Therefore, there is a need in the art to provide improved means for treating allergy. In particular, an object of the present invention resides in providing means that allow treatment of allergy in an efficient, easy and cost effective manner preferably without requiring a physician and without bringing about the negative associations linked with such treatments.